Avalanche Forecast

Issued: Feb 24th, 2018 4:27PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

jmcbride, Avalanche Canada

Cariboos.

Expect new snow and strong winds to form storm slabs and grow cornices. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. Avoid wind loaded areas with pillowy or chalky looking snow.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

TONIGHT: Flurries. Accumulation 5-15 cm. Ridge wind strong to extreme, southwest. Temperature -12. Freezing level valley bottom.SUNDAY: Mostly cloudy, light flurries. Accumulation 2-5 cm. Ridge wind strong, west. Temperature -10. Freezing level valley bottom. MONDAY: Cloudy, flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature -6. Freezing level 600 m. TUESDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southwest. Temperature -5. Freezing level 900 m.

Avalanche Summary

There have been no new reports of avalanches since Wednesday (Feb 21) when a size 2, natural cornice release was reported on a southeast aspect at 1900 m in the northern part of the region.Prior to that on Tuesday, there was a report of a skier triggered size 1.5 soft, wind slab release (25-50 cm deep) on a northeast-facing open, treeline slope at 1900 m, that failed on the mid-February surface hoar layer.Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

About 5 to 15 cm of new snow now covers the old snow interface which consists of sugary facets as well as sun crust on solar aspects and surface hoar on shaded, wind-sheltered slopes.Below the old interface lies another interface, with similar character and distribution that was buried mid-February and is now 25-50 cm below the snow surface. This layer has been reactive in recent snowpack tests and recent avalanches have been reported to have failed on this layer in the past week.Within the mid and lower snowpack are several persistent weak layers that are slowly beginning to show signs of improving but still remain suspect. Two surface hoar/ crust layers buried in January are now 100-150 cm below the snow surface. At least one of these layers can be found on all aspects and elevations.Deeper in the snowpack (150 - 200 cm deep) is a facet/crust/surface hoar layer buried in December that is most prevalent at treeline elevations and below.Near the base of the snowpack is a crust/facet combo layer buried in late November.

Problems

Storm Slabs

New snow and strong winds will create storm slabs in many areas in the alpine, as well as open areas at lower elevations. These slabs may be especially deep and touchy in wind-loaded areas on the leeward (down-wind) side of ridges and convex rolls.

Watch for whumpfing, hollow sounds, and shooting cracks.Be careful with wind loaded slopes, especially near ridge crests and roll-overs.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

Buried weak layers exist within the snowpack and may be reactive to large triggers such as a cornice or storm slab release. Human triggering may also be possible in shallow or thin, rocky, unsupported terrain.

Avoid steep convexities or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Feb 25th, 2018 2:00PM